1. Technical Field
One or more embodiments of the present invention generally relate to systems and processes for cooling a feed gas stream with a single closed-loop mixed refrigerant cycle.
2. Description of Related Art
In recent years, natural gas has become a widely used source of fuel. In addition to its clean burning qualities and convenience, advances in exploration and production technology have permitted previously unreachable gas reserves to become accessible. Because many of these previously unreachable sources of natural gas are remote and are not connected to commercial markets or infrastructure by pipeline, cryogenic liquefaction of natural gas for transportation and storage has become increasingly important. In addition, liquefaction permits long term storage of natural gas, which can help balance out periodic fluctuations in supply and demand.
Several methods for liquefying natural gas are currently in practice. Although the specific configuration and/or operation of each facility may vary depending on, for example, the type of refrigeration system used, the rate and composition of feed gas, and other factors, most commercial facilities generally include similar basic components. For example, most facilities typically include a pretreatment area for removing one or more impurities from the incoming gas stream, a liquefaction zone for liquefying the gas stream, a refrigeration system for providing refrigeration to the liquefaction zone, and a storage and/or loading area for receiving, storing, and transporting the final liquefied product. Overall, the cost to construct and operate these facilities can vary widely, but in general, the cost of the refrigeration portion of the plant can account for up to 30 percent or more of the overall cost of the facility.
Thus, a need exists for an optimized refrigeration system capable of efficiently producing a liquefied gas product at a desired capacity, but with minimum amount of equipment. Ideally, the refrigeration system would be both robust and operationally flexible in order to handle variations in feed gas composition and flow rate, while still requiring minimal capital outlay and operating at the lowest possible cost.